Shots - Health Blog

2:23 pm

Thu October 4, 2012

Scientists Create Fertile Eggs From Mouse Stem Cells

Each of these mouse pups was born from an egg scientists created using embryonic stem cells. It's possible the technology could change future treatment for human infertility.

Katsuhiko Hayashi

Scientists in Japan report they have created eggs from stem cells in a mammal for the first time. And the researchers went on to breed healthy offspring from the eggs they created.

While the experiments involved mice, the work is being met with excitement — and questions — about doing the same thing for humans someday.

"Wow. That's my general reaction," said Hank Greely, a bioethicist at Stanford University who studies stem-cell science. "Repairing hearts, repairing brains, repairing kidneys, that's all good and important, and we'd all love to be able to do that. But this involves making the next generation."

Scientists obtain the versatile cells from embryos. Embryonic stem cells are controversial because researchers destroy the embryos to get them.

But because these stem cells can morph into any cell in the body, there's always been the possibility they could do something especially profound. They could offer a way to create eggs from anyone at any age. That could change how humans reproduce.

In this week's issue of the journal Science, Mitinori Saitou and colleagues at Kyoto University in Japan report they finally achieved that elusive goal.

"This is actually the first time to make eggs from embryonic stem cells and then produce eggs [that] become healthy offspring," Saitou said.

Moreover, Saitou's team did something potentially even more astonishing: They bred healthy mice from eggs made from another type of stem cell known as induced pluripotent stem cells.

These are cells that look essentially identical to embryonic stem cells. But instead of coming from embryos, they can be made from adult cells, such as skin or blood cells. So they don't have any of the ethical baggage of embryonic cells.

"They're gotten to what was our Holy Grail, which is making eggs," said George Daly, a leading stem-cell scientist at Harvard. "It's like cellular alchemy. I mean, they can turn lead into gold here. They can turn skin cells or blood cells into eggs."

The big question, of course, is whether anyone could do the same thing for people. No one knows for sure. And it would surely take a ton of work.

But John Gearhart, a stem-cell pioneer at the University of Pennsylvania, says mice are close enough to humans to think it's probably doable. "I think this will be worked out in time. I don't have any doubt about it," Gearhart said.

And if he's right, then, at the very least, it would be a huge advance for women who are infertile for medical reasons or who have postponed having babies too long.

"If we can make eggs from stem cells, then the biological clock isn't ticking so much for women," Stanford's Greely said.

But that could be just the beginning. The same team previously made sperm from stem cells. So, for example, the power to create sperm or eggs for anyone would be big news to many gay men and lesbians.

And Greely goes even further into territory charted by the book Brave New World. Combined with other techniques, eggs from stem cells could some day make it much easier for parents to pick babies with blue eyes or blond hair, or a talent for sports or music.

Speculation about the possibilities get even more sci-fi. "Any skin cell that you can find on the edge of a coffee cup theoretically could be induced back to being an egg, and a baby could be produced," said Ronald Green, a bioethicist at Dartmouth University.

"When you think about the commercial possibilities of people selling to infertile people babies produced from George Clooney or Jennifer Aniston, or whatever, you have to worry about it," Green said.

Now, it's important to remember that this may end up being nothing more than speculation. And even if it does prove possible, choices like these are probably decades away.

Even so, David Prentice of the Family Research Council says such research "cheapens all life in a way, not just embryonic or fetal life, but babies and the rest of us when we starting treating life as a manufacturing proposition."

But just the possibility is already stirring intense debate about where the power to use stem cells to make eggs might take us. "It's like any other technology," said Daniel Sulmasy, a professor of medicine and ethics at the University of Chicago. "Whatever we've done in human kind — whether it's discovering fire or creating the wheel — you can use these things to do lots of good and you can use them immoral ways," he says.

And I'm Audie Cornish. Scientists in Japan today report they have done something startling - for the first time, they've used stem cells to create eggs. Their experiments involved mice but as NPR's Rob Stein reports, the work is generating a lot of excitement - and questions - about doing the same thing for humans.

ROB STEIN, BYLINE: Ever since scientists discovered human embryonic stem cells, there has been talk these seemingly magical cells could transform society. The latest advance is stirring that kind of talk again. Hank Greely is a bioethicist at Stanford.

HANK GREELY: Wow - that's my general reaction.

STEIN: Greely says the advance goes way beyond all the hopes that stem cells will someday cure diseases.

GREELY: Repairing hearts, repairing brains, repairing kidneys - that's all good and important; and we'd love to be able to do that. But this involves making the next generation.

STEIN: Stem cells can morph into any cell in the body. So there's always been the possibility that they could offer a way to create eggs from anyone, at any age. That could be a game-changer for how humans reproduce.

DR. GEORGE DALEY: They've gotten to what was our holy grail, which is making eggs.

STEIN: George Daley's a leading stem cell scientist at Harvard. He's referring to scientists at Kyoto University. In this week's issue of the journal "Science," the Japanese researchers report they finally achieved that elusive goal - they created eggs from embryonic stem cells from mice. They then used those eggs to breed healthy mice. Next, they did something even more astonishing. They used a different kind of stem cell, to do the same thing; stem cells that look exactly like embryonic stem cells but instead of coming from embryos, these stem cells can be made out of cells like skin, or blood. So they don't come with all the ethical issues swirling around stem cells from embryos. Here's Harvard's George Daley again.

DALEY: It's like cellular alchemy. I mean, they can turn lead into gold here; they can turn skin cells, or blood cells, into eggs.

STEIN: The big question, of course, is whether anyone could do the same thing for people. No one knows, for sure. John Gearhart, a stem cell pioneer at the University of Pennsylvania, says it would surely take a long time; but mice are close enough to humans to think, it's doable.

JOHN GEARHART: I think this'll be worked out, in time. I don't have any doubt about it.

STEIN: And if that's right, then at the very least, it would be a huge breakthrough for women who are infertile for medical reasons, or just because they waited too long to have babies. Here's Stanford bioethicist Hank Greely again.

GREELY: If we can make eggs from stem cells, then the biological clock isn't ticking so much, for women.

STEIN: But that could just be the beginning. This could give scientists an endless supply of eggs to experiment on; create vast egg banks. Greely points out that the same team previously made sperm from stem cells.

GREELY: There are lots of lesbian and gay couples who would be very excited about the possibility, for the first time, of being able to have children who were genetically their own.

STEIN: And Greely goes much, much further. Combined with new genetic techniques, eggs from stem cells could someday make it much easier to pick babies with blue eyes or blonde hair, or a talent for sports or music.

GREELY: It will change the world, if it happens, by giving parents - I hope, parents; potentially, governments or insurers or doctors, or somebody else. But in the U.S., I suspect it will give parents a greater ability to choose the genetic traits of their children.

STEIN: Speculation about the possibilities get even more sci-fi. Ronald Green's a bioethicist at Dartmouth. He says stem cell eggs could even let someone create someone else's baby, without their permission.

RONALD GREEN: Any skin cell that you can find on the edge of a coffee cup, theoretically could be induced back to being an egg; and a baby could be produced. When you think about the commercial possibilities of people selling, to infertile people, babies produced from George Clooney or Jennifer Aniston or whatever, you have to worry about it.

STEIN: Now, it's important to remember that none of this may end up being possible. And even if it is possible, it's probably decades away. But just the possibility is already stirring intense debate about whether scientists should even be trying to unleash the power of stem cells, to manipulate human reproduction in these ways.